History Bumber-WAC was the first large two-stage liquid-propellant rocket. The
first stage was a captured german V-2
rocket. The warhead was removed and
the nose rebuilt to a launching compartment with blast ports.

The second stage was a modified WAC Corporal sounding
rocket. The WAC was equipped with four fins with 50% more total area, than
the original WAC.

After some test launches the fifth Bumber-WAC 5 was
launched On February 24, 1949 from White Sands proving ground. It reached
a record altitude of 393 km/244 miles. This record held for 8 years until
1957.

Bumper-Wac number 7 and 8 were flown for speed not
for altitude. There was a risk that parts of the rocket would land outside
the White Sands area. Instead the Bumper-Wac tests were moved to a
sparsely populated costal area, called Cape Canaveral. Bumper-WAC 7 was
the first rocket to be launched for the cape.

The program was officially concluded in July 1950.

Sources:

Books and
articles:
Germany's Secret Weapons by Roger Ford

V-2 Ballistic Missile 1942-1952 by Steven J. Zagola

Dawn of the Rocket Age by Joachim Engelmann

The Rocket - The History and Development of Rocket and Missile
Technology by David Baker.